I would do multi segment flights for this trip and restructure it a little. You could, for cheap, fly in to Barcelona and fly out of London. Look on Kayak at their multi destination flights and on other websites for the same. If you were able to find a good deal on that you could go to Ibiza from Barcelona, on a flight or ferry, then go straight from ibiza to Rome on a flight with ryanair. Then you would just go about the rest of your trip and end in London. Although it may be easier to just do roundtrip out of Barcelona and fly straight from London to Ibiza. You probably still want to fly from Barcelona to Rome though.

Well we already have our flight and planned it this way I wish we would have waited but this I think will work out , we will learn how to do it better nexttime we go to Europe . We will realize all the stuff we did wrong on this trip and our next trip will be more put together than thia one haha